Error correction method and data reproduction device

ABSTRACT

The error correction processing includes: data reproduction processing of reproducing recording data, constituted by a plurality of data units each made of a plurality of bits, from a recording medium sequentially; error correction processing of performing error correction in the row direction and error correction in the column direction at least once for an error correction code block that has the reproduced recording data arranged in the row direction over a plurality of rows; determination processing of determining whether uncorrectable data is left behind after execution of the error correction processing; and erasure correction processing of performing, when it is determined that uncorrectable data is left behind, column-direction error correction considering data constituting at least one row of the error correction code block as erasure data, even in cases where uncorrectable data in the error correction in the row direction is not left behind.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of PCT International ApplicationPCT/JP2010/003883 filed on Jun. 10, 2010, which claims priority toJapanese Patent Application No. 2009-139279 filed on Jun. 10, 2009. Thedisclosures of these applications including the specifications, thedrawings, and the claims are hereby incorporated by reference in theirentirety.

BACKGROUND

The present disclosure relates to an error correction method, and a datareproduction device, of performing error correction for recording dataread from a recording medium.

In conventional optical disc reproduction devices, recording data readfrom an optical disc is stored into a buffer memory for error correctionprocessing and transfer to a host computer. In such optical discreproduction devices, the addresses of frames, sectors, and ECC blocksin the buffer memory are specified by detecting various types of syncpatterns (sync patterns included in frames, frame sync codes indicatingthe heads of sectors, and IDs indicating head sectors of ECC blocks).

A data reproduction device disclosed in Japanese Patent No. 3459225(Patent Document 1) reinforces interpolation of various types of syncpatterns for preventing failure in correspondence between addresses anddata in a buffer memory due to detection omission, false detection,abnormal interpolation, etc. of sync patterns that might occur fromfingerprints, claws, etc. on an optical disc.

A data reproduction device disclosed in Japanese Patent No. 4143452(Patent Document 2) is provided with an address generation means that,when a sync code is not detected for a predetermined number of timesconsecutively, interpolates frame addresses for a plurality of framesappearing during and after this non-detection time period, and performsPO erasure correction for a frame, out of the plurality of frames, inwhich the frame address generated by the interpolation does not matchwith a frame address calculated based on only the sync code.

SUMMARY

In Patent Document 1, the correspondence between addresses and data inthe buffer memory can be secured. However, in the case that therecording quality of the optical disc is poor, data stored in the buffermemory may be incorrect because of suspension and restart of datarecording at the time of data edition and rewrite, etc., and thus maynot be reproduced normally even if error correction is performed. Such aproblem tends to occur, in particular, when data of at least one sectorhas become incorrect because frames and sectors have been resynchronizedby interpolation while an anomaly of a sync code has been missed.

In Patent Document 2, as in Patent Document 1, the correspondencebetween addresses and data in the buffer memory can be secured, and theposition at which an anomaly of a sync code has occurred can beconsidered as a target of error correction. However, in the cases thatthe recording quality of the optical disc and the quality of thereproduced signal are poor and that suspension and restart of datarecording are performed at the time of data edition and rewrite, forexample, whether data in question is actually the data in the errorcorrection target block cannot be determined if the sync code can beread as a different sync code and if data in the correction block iswrong due to recording deviation. In such a case, data may not bereproduced normally even if error correction is performed.

In view of the problems described above, it is an objective of thepresent disclosure to reproduce data recorded on a recording mediumnormally.

To attain the above objective, the present disclosure includes: datareproduction processing of reproducing recording data, constituted by aplurality of data units each made of a plurality of bits, from arecording medium sequentially while detecting a sync pattern included ineach data unit; error correction processing of performing errorcorrection in a row direction and error correction in a column directionat least once for an error correction code block that has the recordingdata reproduced in the data reproduction processing arranged in the rowdirection over a plurality of rows; determination processing ofdetermining whether uncorrectable data is left behind after execution ofthe error correction processing; and erasure correction processing ofperforming, when it is determined that uncorrectable data is left behindin the determination processing, error correction in the columndirection considering data constituting at least one row of the errorcorrection code block as erasure data, even in cases where uncorrectabledata in the error correction in the row direction is not left behind.

According to the present disclosure, when uncorrectable data is leftbehind, error correction in the column direction is performedconsidering a sector having the uncorrectable data left behind in anerror correction code block as erasure data, even in cases whereuncorrectable data in the error correction in the row direction is notleft behind. Therefore, in the case that a data unit made of a pluralityof bits arranged in the row direction becomes incorrect, which may occurwhen it is determined that an anomaly has occurred in a sync pattern andthus resynchronization is performed, such error correction that has beenconventionally unattainable can be attained, and thus data can bereproduced normally with higher probability.

Thus, the present disclosure has an advantage of permitting such errorcorrection that has been conventionally unattainable and thus being ableto reproduce data normally with higher probability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a sector structure of a DVD.

FIG. 2 is a view illustrating an error correction code block of a DVD.

FIG. 3 is a block diagram of a data reproduction device of the firstembodiment of the present disclosure.

FIG. 4 is a flowchart showing the operation of the data reproductiondevice of the first embodiment of the present disclosure.

FIG. 5 is a block diagram of a data reproduction device of the secondembodiment of the present disclosure.

FIG. 6 is a flowchart showing the operation of the data reproductiondevice of the second embodiment of the present disclosure.

FIG. 7 is a block diagram of a data reproduction device of the thirdembodiment of the present disclosure.

FIG. 8 is a block diagram of a data reproduction device of the fourthembodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described hereinafter withreference to the accompanying drawings. Note that, in the embodiments tofollow, components having similar functions are denoted by the samereference characters and will not be described repeatedly.

First Embodiment

A data reproduction device of the first embodiment of the presentdisclosure reproduces recording data recorded on a digital versatiledisc (DVD) 100 (see FIG. 3) as an optical disc.

<Sector Structure of DVD 100>

The sector structure of the DVD 100 will be described with reference toFIG. 1.

As recording data on the DVD 100, data of 91 bytes and a sync pattern(SYNC) of two bytes indicating the head of the data constitute one frame(second data group).

A total of 26 frames constitute one sector (first data group). The firstfour bytes of data of the sector is used for the sector number(identification (ID)). The position of a frame (frame address) in thesector can be specified uniquely by a combination of sync patterns oftwo consecutive frames. Since the first sync pattern (SY0), out of the2-byte sync patterns, is placed only at the head of the sector, theposition of SY0 can be specified as the head of the sector.

<Error Correction Code Block>

Next, an error correction code (ECC) block will be described withreference to FIG. 2. Data of 182 bytes (91 bytes+91 bytes) of two framesfrom the head of each sector constitute one row. The last 10 bytes ofeach row are used as Parity of Inner-Code (PI), and the thirteenth rowof each sector is used as Parity of Outer-Code (PO). In other words, a10-byte parity (PI) by Reed-Solomon (RS) Coding is added to one row ofdata of 172 bytes lined in the lateral direction, and a 16-byte parity(PO) by RS Coding is added to one column of data of 192 bytes lined inthe vertical direction.

One ECC block, including 16 sectors, is recorded on the DVD 100 in thelateral direction sequentially. The number of each sector (sectoraddress) in the ECC block can be specified by the 4-byte data at thehead of the sector. This ECC block is the unit of error correction.

<Configuration of Data Reproduction Device>

As shown in FIG. 3, the data reproduction device of the first embodimentof the present disclosure includes a data reproduction section 101, amemory 102, an erasure correction section 103, and a determinationsection 106.

The data reproduction section 101 reproduces recording data from the DVD100 sequentially while detecting the sync pattern (SY0) included in eachsector and the sync pattern (SY0-SY7) included in each frame. There is apossibility that the data reproduction section 101 may detect SYNC at aposition deviated from the position where it should be due to a defect,dust, etc. on the DVD 100. To prevent such an occurrence, the datareproduction section 101 interpolates position data (e.g., a frameaddress, a sector address, SYNC, and SY0) that has not been recordednormally on the DVD 100, based on position data obtained by reproducingthe recording data again from the DVD 100 sequentially, and outputs theresultant (interpolated) data, and also outputs interpolationinformation indicating whether interpolation has been made for eachposition data unit (this is not shown in FIG. 3). For example, SYNC ischecked at any time during reading of recording data, and, if SYNC ismissing or deviated, SYNC data is interpolated at the SYNC missingposition. In this way, the data reproduction section 101 can read therecording data.

The memory 102 holds the recording data reproduced by the datareproduction section 101.

The erasure correction section 103 executes an error correction step ofperforming error correction in the row direction (PI correction) anderror correction in the column direction (PO correction) at least oncefor the ECC block that includes the recording data reproduced by thedata reproduction section 101 arranged in the row direction sequentiallyover a plurality of rows.

The determination section 106 determines whether uncorrectable data isleft behind after the execution of the error correction step by theerasure correction section 103.

If the determination section 106 determines that uncorrectable data isleft behind, the erasure correction section 103 executes erasurecorrection processing of performing error correction in the columndirection, considering data of 13 rows in the ECC block as erasure data,irrespective of the result of the error correction in the row direction.That is, even in cases where uncorrectable data in the error correctionin the row direction is not left behind, the erasure correction section103 performs error correction in the column direction, considering the13-row data as erasure data, when the determination section 106determines that uncorrectable data is left behind.

Specifically, the erasure correction section 103 includes an errorcorrection portion 104 and an erasure setting portion 105.

The error correction portion 104 performs error correction for therecording data held in the memory 102. Also, the error correctionportion 104 performs error correction in the column direction,considering data in rows specified by erasure setting information set bythe erasure setting portion 105 as erasure data.

The erasure setting portion 105 sets the erasure setting informationthat specifies 13 rows in the ECC block (a column of 13 PI codes) whenit is determined that uncorrectable data is left behind by thedetermination section 106.

<Operation of Data Reproduction Device>

The operation of the data reproduction device configured as describedabove will be described with reference to FIG. 4.

In (S1001), first, the data reproduction section 101 reproducesrecording data from the DVD 100, one ECC block at a time, and stores thedata into the memory 102. Then, n=1 is set.

In (S1002) and (S1003), the error correction portion 104 performs PIcorrection and PO correction as conventionally done for an ECC blockthat has the recording data reproduced by the data reproduction section101 and held in the memory 102 arranged in the row direction. At thistime, the error correction portion 104 enables or disenables an errorcorrection control signal in accordance with whether the errorcorrection was possible or not.

When the error correction control signal is enabled (rises), in (S1004),the determination section 106 determines whether uncorrectable data isleft behind after the PO correction in (S1003). If there isuncorrectable data left behind, the determination section 106 enables(raises) an erasure setting control signal, to instruct the erasuresetting portion 105 to set erasure setting information in (S1005). Inresponse to this instruction, the erasure setting portion 105 setserasure setting information specifying 13 lines of PI codes, i.e., then-th to (n+12)th rows in the ECC block, and then n=n+13 is set.

Thereafter, in (S1003), the error correction portion 104 reads recordingdata from the memory 102 and performs PO correction for the read data,considering the data of the rows specified by the erasure settinginformation as erasure data. Once the error correction processing isterminated without problems, i.e., once the determination section 106determines that there is no uncorrectable data left behind, the errorcorrection portion 104 disenables (lowers) the error correction controlsignal, and the processing returns to (S1001). If the determinationsection 106 determines again that there is uncorrectable data leftbehind, the erasure setting portion 105 sets again erasure settinginformation specifying 13 lines of PI codes. The erasure settinginformation set this time specifies lines of PI codes descending by 13rows from the lines of PI codes specified by the erasure settinginformation set last time.

In (S1001) (data reproduction step), if it is determined that an anomalyhas occurred in a SYNC code and resynchronization is performed using theSYNC code, data read by the data reproduction section 101 will becomeincorrect, as in the conventional case. In this case, if data isincorrect because of a poor data recording state, failure at a datawrite link, etc., for example, the PO correction in (S1003) may fail toterminate normally, leaving uncorrectable data behind, although nouncorrectable data is left behind in the PI correction in (S1002). Thereason why the determination section 106 detects that uncorrectable datais left behind after the PO correction in (S1004) although the PIcorrection has terminated normally is considered that incorrect data of13 rows of one sector has been generated due to the resynchronizationusing the SYNC code. Therefore, by performing PO correction, consideringdata of 13 rows corresponding to one sector as erasure data,sequentially from the head of the ECC block read in (S1001), it ispossible to prevent the occurrence of failing to reproduce data normallydue to data error of one sector. In other words, by repeating POcorrection and erasure setting the maximum 16 times (208 (number of rowsof the ECC block)÷13 (number of rows of one sector)), the possibilitythat error correction can be completed normally can be enhanced.

When the memory quality of the DVD 100 is poor, or when data is editedor rewritten, there is a possibility that data stored in the buffermemory is incorrect due to wrong resynchronization caused by erroneousacquisition of SYNC even though the data stored in the buffer memorycorresponds to its address. In this embodiment, however, since the errorcorrection capability is enhanced as described above, the recording datarecorded on the DVD 100 can be reproduced correctly with higherprobability even when the data stored in the buffer memory is incorrect.

In this embodiment, although the number of rows specified by the erasuresetting information from the erasure setting portion 105 is 13, it canbe any number equal to or more than one if only data of such a number ofrows can be corrected at one time of error correction.

In this embodiment, PO correction is performed in (S1003) immediatelyafter the setting of the erasure setting information in (S1005).Alternatively, the processing may return to (S1001) after the setting ofthe erasure setting information, to read recording data. In other words,after the determination section 106 determines that there isuncorrectable data left behind and by the time when the erasurecorrection section 103 executes the erasure correction processing, thedata reproduction section 101 may reproduce recording data again fromthe DVD 100 sequentially. The flow of operation in this case will berepeating retry of reproduction with the erasure setting informationchanged, like data read→PI correction→PO correction→erasure setting→dataread→PI correction→PO correction→erasure setting→data read.

Also, in this embodiment, after the data reproduction section 101 readsdata and stores the data into the memory 102, the error correctionportion 104 performs PI correction and PO correction. Alternatively,after the data reproduction section 101 reads data and the errorcorrection portion 104 performs PI correction, the PI-corrected data maybe stored into the memory 102, and thereafter the error correctionportion 104 may perform PO correction.

Second Embodiment

As shown in FIG. 5, a data reproduction device of the second embodimentof the present disclosure includes a correction processing section 201and a selection section 202 in addition to the components of the datareproduction device of the first embodiment.

The correction processing section 201 executes the conventional errorcorrection. More specifically, the correction processing section 201executes an error correction step of performing error correction in therow direction (PI correction) and error correction in the columndirection (PO correction) at least once for the ECC block that has therecording data reproduced by the data reproduction section 101 arrangedin the row direction sequentially over a plurality of rows.

The selection section 202 selects either error correction informationoutput from the error correction portion 104 or error correctioninformation (the position of error correction and correct data after theerror correction) output from the correction processing section 201,based on a select signal indicating which error correction information,from the error correction portion 104 or from the correction processingsection 201, is currently coming. Using the selected error correctioninformation, error correction is performed for data stored in the memory102. In other words, the selection section 202 selects which one,correction by the erasure correction section 103 (first correctionprocessing) or correction by the correction processing section 201(second correction processing), should be executed.

The operation of the data reproduction device of this embodimentconfigured as described above will be described with reference to FIG.6.

First, in (S1001), the data reproduction section 101 reads recordingdata from the DVD 100, one ECC block at a time, and stores the data intothe memory 102. Subsequently, in (S1002), (S1003), (S2001), and (S2002),the error correction portion 104 and the correction processing section201 read data stored in the memory 102 and perform PI correction and POcorrection. The correction processing section 201 executes PI correctionand PO correction at least once, and then shifts its processing to thenext ECC block. Note that the number of times of execution of PIcorrection and PO correction is not limited to one, but the correctionprocessing section 201 may perform PI correction and PO correction aplurality of times for data having many errors.

In this embodiment, after the data reproduction section 101 reads dataand stores the data into the memory 102, the error correction portion104 and the correction processing section 201 perform PI correction andPO correction. Alternatively, after the data reproduction section 101reads data and the error correction portion 104 or the correctionprocessing section 201 performs PI correction, the PI-corrected data isstored into the memory 102, and thereafter the error correction portion104 and the correction processing section 201 may perform PO correction.

If the determination section 106 enables (raises) the erasure settingcontrol signal in (S1004), the erasure setting portion 105 sets erasuresetting information in (S1005) as in the first embodiment. Thereafter,the error correction portion 104 performs PO correction, wherebyuncorrectable data can be rendered error correctable, and thus therecording data can be reproduced normally with more reliability.

The processing in (S1000) including the steps (S1002) to (S1005) (firstcorrection processing) and the processing (S2000) including the steps(S2001) and (S2002) (second correction processing) are executed inparallel.

In (S2004), the selection section 202 selects either the processingresult in (S1000) and the processing result in (S2000). Morespecifically, the selection section 202 selects either error correctioninformation output from the error correction portion 104 or errorcorrection information (the position of error correction and correctdata after the error correction) output from the correction processingsection 201, based on a select signal indicating which error correctioninformation, from the error correction portion 104 or from thecorrection processing section 201, is currently coming. Using theselected error correction information, error correction is performed fordata stored in the memory 102. The error correction portion 104 disables(lowers) the error correction control signal at the time of terminationof the error correction processing without problems.

In order to respond to a situation where the error correction portion104 must perform a number of error corrections in a short time, pseudospace may be provided for holding a plurality of erasure settinginformation units, erasure setting control signals, etc.

This embodiment can provide an advantage that the number of retries canbe reduced by performing corrections different in error correctionconditions using the correction processing section 201 that performs theconventional error correction and the error correction portion 104 inparallel, in addition to the advantage of enhancing the error correctioncapability in the first embodiment.

In this embodiment, data stored in the memory 102 is read by the errorcorrection portion 104 and the correction processing section 201.Alternatively, the error correction portion 104 may be placed downstreamof the correction processing section 201. This eliminates the necessityof the error correction portion 104 performing the conventional errorcorrection and further can reduce the number of retries.

Third Embodiment

FIG. 7 shows a data reproduction device of the third embodiment of thepresent invention.

The data reproduction device of this embodiment includes a specificationsection 302 that specifies the position of a data unit includinginterpolated position data in an ECC block based on position data andinterpolation information output from the data reproduction section 101.

The specification section 302 includes a position data interpolationdetection portion 303 and a position data determination portion 304.

The position data interpolation detection portion 303 retrievesinterpolated position data based on position data and interpolationinformation output from the data reproduction section 101.

The position data determination portion 304 specifies where theinterpolated position data is in the ECC block, and outputs positioninformation indicating the position of the interpolated position data inthe ECC block.

Also, an erasure setting portion 306 of an erasure correction section305 sets erasure setting information based on, not only thedetermination result of the determination section 106, but also theposition information output from the position data determination portion304.

The operation of the data reproduction device of this embodimentconfigured as described above will be described.

First, the operation of setting erasure setting information using asector address, out of the position data output from the datareproduction section 101, will be described. When receiving sectoraddresses, SY0, and interpolation information from the data reproductionsection 101, the position data interpolation detection portion 303extracts a sector address at the position where the interpolationinformation indicates presence of interpolation (rises) at the timing ofSY0, and discards any sector address at the position where theinterpolation information indicates absence of interpolation (falls).Note that the sector address and SY0 are position data indicating theposition of a sector (data unit) on the DVD 100.

Then, the position data determination portion 304 specifies the state(position information in the ECC block, i.e., sector addresses in theECC block) of the reproduced data based on the data output from theposition data interpolation detection portion 303. Thereafter, theerasure setting portion 306 sets erasure setting information using theposition information output from the position data determination portion304 when the erasure setting control signal output from thedetermination section 106 is in the enabled state (high). The erasuresetting information set at this time specifies a specific sector in theECC block, which corresponds to 13 rows (1 sector=13 rows). Note howeverthat, if interpolation has been performed two or more times, rows of twoor more multiple of 13 may be specified in some cases. Morespecifically, the erasure setting information set at this time specifies13 rows corresponding to a sector where at least either its sectoraddress or SY0 has been interpolated.

Next, the operation of setting erasure setting information using a frameaddress will be described. When receiving frame addresses, SYNC, andinterpolation information from the data reproduction section 101, theposition data interpolation detection portion 303 extracts a frameaddress at the position where the interpolation information indicatespresence of interpolation (rises) at the timing of SYNC, and discardsany frame address at the position where the interpolation informationindicates absence of interpolation (falls). Note that the frame addressand SYNC are position data indicating the position of a frame (dataunit) on the DVD 100.

Then, the position data determination portion 304 specifies the state(position information in an ECC block, i.e., frame addresses in the ECCblock) of the reproduced data based on the data output from the positiondata interpolation detection portion 303. Thereafter, the erasuresetting portion 306 sets erasure setting information using the positioninformation output from the position data determination portion 304 whenthe erasure setting control signal output from the determination section106 is in the enabled state (high). The erasure setting information setat this time specifies specific lines of PI codes in the ECC block. Morespecifically, the erasure setting information set at this time specifiesa row including a frame where at least either its frame address or SYNChas been interpolated.

As described above, in this embodiment, it is possible to estimate therecording position of incorrect data using an interpolated sectoraddress or frame address and perform error correction considering dataat the estimated recording position as erasure data. Therefore, comparedwith the first embodiment, the number of times of error correctionperformed at and after setting of erasure setting information by theerasure setting portion 306 can be widely reduced, and thus the timerequired for reproduction of data can be shortened. Also, in the case ofcorrection processing following the flow of data read→PI correction→POcorrection→specification of erasure data position→data read→PIcorrection→erasure setting→PO correction→next data read (retryprocessing), the time required for reproduction of data can be shortenedfurther effectively with reduction in the number of times of errorcorrection.

In this embodiment, an example of operation of setting erasure settinginformation using either a sector address or a frame address isdescribed. Alternatively, both the sector address and the frame addressmay be used to calculate the position data in one ECC block (output ofthe position data determination portion 304) more correctly, setting theerasure setting information using both addresses. This can furthershorten the time required for error correction.

In this embodiment, the erasure setting portion 306 uses the positioninformation output from the position data determination portion 304 whenthe erasure setting control signal output from the determination section106 is in the enabled state (high). Alternatively, interpolationinformation output from the position data determination portion 304 maybe used.

Although sector addresses, frame addresses, SYNC, and SY0 are used asexamples of the position data in this embodiment, other types ofposition information and sync signals may be used in place of the aboveexamples.

Fourth Embodiment

As shown in FIG. 8, a data reproduction device of the fourth embodimentincludes a recording position information acquisition section 401 inaddition to the components of the data reproduction device of the thirdembodiment, and includes a specification section 402 in place of thespecification section 302 in the third embodiment.

The recording position information acquisition section 401 readsphysical information (e.g., CAPA, LPP, etc.) written previously on theDVD 100, and converts the physical information to a physical addressthat is recording position information on the DVD 100.

The specification section 402 includes a recording positiondetermination portion 403 in addition to the components of thespecification section 302 in the third embodiment.

The recording position determination portion 403 compares the physicaladdress acquired by the recording position information acquisitionsection 401 with the state (position information in the ECC block) ofreproduced data output from the position data determination portion 304using the sync pattern detected by the data reproduction section 101,and specifies the correct state (position information in the ECC block)of the reproduced data based on the comparison result.

For example, the recording position determination portion 403 receives async pattern (e.g., SYNC and SY0) detected by the data reproductionsection 101 and output from the position data interpolation detectionportion 303, a physical address acquired by the recording positioninformation acquisition section 401, and a sector address output fromthe position data determination portion 304, and compares the physicaladdress with the sector address (an example of a reproduced data statesignal) in the ECC block at the timing of the sync pattern. If thesector address output from the position data determination portion 304is different from the sector address in the ECC block calculated basedon the physical address acquired by the recording position informationacquisition section 401 and the recording position information recordedpreviously on the DVD 100, the recording position determination portion403 corrects the sector address output from the position datadetermination portion 304 into the sector address calculated based onthe physical address and the recording position information. The erasuresetting portion 306 sets erasure setting information based on thecorrected sector address.

In this embodiment, in which erasure setting information is generatedusing the position information recorded on the DVD 100, the errorposition can be specified more precisely, and thus the number of timesof repetition of error correction can be reduced. As a result, the timerequired for data reproduction can be shortened. Also, in the case ofcorrection processing following the flow of data read→PI correction→POcorrection→storing of recording position and erasure settinginformation→data read→PI correction→erasure setting→PO correction→nextdata read (retry processing), the time required for data reproductioncan be shortened further effectively with reduction in the number oftimes of error correction.

The correction processing by the recording position determinationportion 403 as described above is applicable, not only to the sectoraddress, but also to other types of position information such as theframe address. When both the sector address and the frame address areused for setting of erasure setting information, the correctionprocessing by the recording position determination portion 403 may beperformed for both the sector address and the frame address.

Although the DVD 100 is used as the recording medium in the first tofourth embodiments, the present disclosure is also applicable to use ofrecording media other than the DVD 100.

The error correction method and the data reproduction device of thepresent disclosure have an advantage of permitting such error correctionthat has been conventionally unattainable and thus being able toreproduce data normally with higher probability, and therefore areuseful as an error correction method, and a data reproduction device, ofperforming error correction for recording data read from a recordingmedium.

What is claimed is:
 1. An error correction method, comprising: a datareproduction step of reproducing recording data, constituted by aplurality of data units each made of a plurality of bits, from arecording medium sequentially while detecting a sync pattern included ineach data unit; an error correction step of performing error correctionin a row direction and error correction in a column direction at leastonce for an error correction code block in which the plurality of dataunits reproduced in the data reproduction step are arranged in the rowdirection over a plurality of rows; a determination step of determiningwhether uncorrectable data is left behind after execution of the errorcorrection step; and an erasure correction step of performing, when itis determined that uncorrectable data is left behind in thedetermination step, error correction in the column direction consideringdata constituting at least one row of the error correction code block aserasure data, even in a case where uncorrectable data in the errorcorrection in the row direction is not left behind.
 2. The errorcorrection method of claim 1, wherein in the data reproduction step,recording data of a plurality of error correction code blocks isreproduced, first correction processing and second correction processingare performed in parallel, the first correction processing beingexecuting the error correction step, the determination step, and theerasure correction step and the second correction processing beingexecuting only the error correction step, and the method furthercomprises a selection step of selecting the first correction processingor the second correction processing to be executed for each of the errorcorrection code blocks.
 3. The error correction method of claim 1,further comprising: when it is determined that uncorrectable data isleft behind, a second reproducing step of reproducing the recording dataagain from the recording medium sequentially by the time when theerasure correction processing is executed.
 4. The error correctionmethod of claim 1, wherein: each data unit includes position dataindicating a position of the each data unit, the method furthercomprises: an interpolating step of interpolating position data that hasnot been recorded normally on the recording medium based on positiondata obtained by reproducing the recording data again from the recordingmedium sequentially; an output step of outputting the interpolatedposition data, and interpolation information indicating whetherinterpolation has been made for each position data; and a specificationstep of specifying the position of a data unit including theinterpolated position data in the error correction code block based onthe position data and the interpolation information, and data consideredas erasure data in the erasure correction step is data of a rowincluding the data unit of which the position has been specified in thespecification step.
 5. The error correction method of claim 4, whereinthe error correction code block is constituted by a plurality of firstdata groups, and each of the first data groups is constituted by aplurality of second data groups, the data unit is the first data group,and the position data indicates the position of the first data group inthe error correction code block.
 6. The error correction method of claim4, wherein the error correction code block is constituted by a pluralityof first data groups, and each of the first data groups is constitutedby a plurality of second data groups, the data unit is the second datagroup, and the position data indicates the position of the second datagroup in the first data group.
 7. The error correction method of claim4, further comprising: a recording position information acquisition stepof acquiring a physical address recorded on the recording medium,wherein the physical address acquired in the recording positioninformation acquisition step is compared with the position datainterpolated in the data reproduction step using the sync patterndetected in the data reproduction step, and specifying the position ofthe data unit including the interpolated position data in the errorcorrection code block based on the comparison result.
 8. A datareproduction device comprising: a data reproduction section configuredto reproduce recording data, constituted by a plurality of data unitseach made of a plurality of bits, from a recording medium sequentiallywhile detecting a sync pattern included in each data unit; an erasurecorrection section configured to execute an error correction step ofperforming error correction in a row direction and error correction in acolumn direction at least once for an error correction code block inwhich the plurality of data units reproduced by the data reproductionsection arranged in the row direction over a plurality of rows; and adetermination section configured to execute a determination step ofdetermining whether uncorrectable data is left behind after execution ofthe error correction step, wherein the erasure correction sectionexecutes, when the determination section determines that uncorrectabledata is left behind, erasure correction processing of performing errorcorrection in the column direction considering data constituting atleast one row of the error correction code block as erasure data, evenin a case where uncorrectable data in the error correction in the rowdirection is not left behind.
 9. The data reproduction device of claim8, wherein when the determination section determines that uncorrectabledata is left behind, the data reproduction section reproduces therecording data again from the recording medium sequentially by the timewhen the erasure correction section executes the erasure correctionprocessing.
 10. The data reproduction device of claim 8, furthercomprising: a correction processing section configured to execute theerror correction step; and a selection section configured to selecteither a combination of the error correction step by the erasurecorrection section, the determination step by the determination section,and the erasure correction processing by the erasure correction sectionor the error correction step by the correction processing section. 11.The data reproduction device of claim 8, wherein each data unit includesposition data indicating a position of the each data unit, the datareproduction section interpolates position data that has not beenrecorded normally on the recording medium based on position dataobtained by reproducing the recording data again from the recordingmedium sequentially and outputs the interpolated position data, and alsooutputs interpolation information indicating whether interpolation hasbeen made for each position data, the data reproduction device furthercomprises a specification section configured to specify the position ofa data unit including the interpolated position data in the errorcorrection code block based on the position data and the interpolationinformation output from the data reproduction section, and dataconsidered as erasure data by the erasure correction section is data ofa row including the data unit of which the position has been specifiedby the specification section.
 12. The data reproduction device of claim11, wherein the error correction code block is constituted by aplurality of first data groups, and each of the first data groups isconstituted by a plurality of second data groups, the data unit is thefirst data group, and the position data indicates the position of thefirst data group in the error correction code block.
 13. The datareproduction device of claim 11, wherein the error correction code blockis constituted by a plurality of first data groups, and each of thefirst data groups is constituted by a plurality of second data groups,the data unit is the second data group, and the position data indicatesthe position of the second data group in the first data group.
 14. Thedata reproduction device of claim 11, further comprising: a recordingposition information acquisition section configured to acquire aphysical address recorded on the recording medium, wherein thespecification section compares the physical address acquired by therecording position information acquisition section with the positiondata interpolated by the data reproduction section using the syncpattern detected by the data reproduction section, and specify theposition of the data unit including the interpolated position data inthe error correction code block based on the comparison result.